This title and <meta name="assert"> is the same as ...-test-001.html, but it's a different (negative) test which is confusing. You should:

- Put this test and -test-001.html in the same file.
- Change the filename to reflect the test, something like custom-element-name-validity.html or something like that (you can probably come up with something better.)

I think it would be fine if that file contained two tests, one for the positive names, one for the negative names. The only downside of this approach is that the first error will mask subsequent errors. But from the point of view of using the % of passing tests as an indication of performance, these more coarsely-grained tests seem more accurate.